In infrared spectrometers, a beam of infrared radiation from a source is directed through a series of mirrors or other focusing elements onto a sample held in a holder. The radiation transmitted through or reflected from the sample is then collected and directed onto a detector. In Fourier Transform Infrared (FTIR) spectroscopy, the output signal from the detector is analyzed with known computer processing techniques to derive information concerning the structure and composition of the sample.
In typical FTIR spectroscopy instruments, a single sample is held in position in a focused infrared beam by a holding fixture. To change a sample, the operator removes the first sample from the holder and inserts the new sample and then initiates a new scan by the instrument. If many different samples are to be analyzed, the procedures involved in changing samples in the instrument result in a substantial waste of the operator's time as well as reducing the available productive operating time of the instrument. Although automatic sample changers are known and used with other types of spectroscopic equipment, automatic sample changers have not commonly been used in FTIR spectroscopy. Because of the relatively limited number of these specialized instruments that are produced, construction of automatic sample changers especially adapted for FTIR spectrometers has not been economically feasible. The automatic sample changing apparatus used in other types of spectroscopy is generally not adaptable to use with FTIR spectrometers because of limitations of space and positioning required with the FTIR instruments. In addition, each manufacturer of present sample changers utilizes a distinct sample holder which is adapted to the particular sample changer made by the manufacturer, limiting the interchangeability of sample holders in different changers. The presently available automatic changers used in general spectroscopy typically have a capacity of about 30 sample holders, are limited to positioning the sample holders sequentially, cannot select a particular sample among the various samples, and are generally not capable of testing a particular sample or samples more than once, if desired.